The invention relates to a microwave-enhanced sputtering configuration including a vacuum chamber, a target in the vacuum chamber which is connected to an electrode connected to a power supply, a magnetic device whose magnetic field exits from the target and again enters into it, a microwave which is guided into the region of the target characterized by an electromagnet placed around the target.
The application of thin layers is required in numerous fields of technology. For example, glass panes are coated in order to provide them with special properties or watch cases comprising a less noble material are coated with a layer comprising a noble material.
For the application of thin layers on substrates, processes have already been suggested of which only electroplating and coating out of a plasma shall be mentioned. Coating out of a plasma has gained increasingly in importance in the last years because it permits a multiplicity of materials as coating material.
In order to generate a plasma suitable for coating, various processes have also been suggested. Of these processes the cathode sputtering process, also referred to as sputtering, is of great interest because of its high coating rates. The coating rates can still be increased in sputtering if a microwave is radiated into the volume in front of the sputtered cathode.
Several devices for a microwave-enhanced sputtering are already known (U.S. Pat. No. 4,610,770, U.S. Pat. No. 4,721,553, DE-A-3,920,834). The microwaves are herein introduced into the plasma region either parallel or perpendicularly or at a given angle to the substrate surface. Through the cooperation of the magnetic field of the magnetron with the microwaves an electron cyclotron resonance (ECR) is established which intensifies the ionization of the plasma particles.
Of disadvantage in most known devices is, however, that the ECR condition occurs in the proximity of the sputter cathode where the excitation of the particles is not as necessary as in the region of the substrate. In order to remedy this disadvantage, in the device according to DE-A-3 920 834 the microwave is radiated onto a substrate which, in turn, is penetrated by the field lines of a permanent magnet. In this way the ECR condition is fulfilled directly above the substrate. In this known device, however, a plasma discharge can only take place up to a given minimum voltage and up to a given pressure. Even with very strong magnetic fields at the target surface, the plasma ignition voltage can not be lowered further. But high discharge voltages lead to undesirable effects, such as for example, the inclusion of noble gases into the substrate structure or to radiation damage.
The invention is therefore based on the task of extending the working range of magnetron cathode discharges toward low discharge voltages and/or working pressures.